Add an extractor for rutube.ru (closes #1136)

It downloads with a m3u8 manifest, requires ffmpeg.

youtube_dl/extractor/__init__.py

@@ -102,6 +102,7 @@ from .ro220 import Ro220IE
 from .rottentomatoes import RottenTomatoesIE
 from .roxwel import RoxwelIE
 from .rtlnow import RTLnowIE
+from .rutube import RutubeIE
 from .sina import SinaIE
 from .slashdot import SlashdotIE
 from .slideshare import SlideshareIE